Hello, I am considering a purchase of ODROID-U2. I have RPi now and I do not like that a patched kernel needs to be used, that there are no drivers / firmware in the portage tree. So I wanted to ask: is ODROID-U2 any better when it comes to this aspect (being able to run with an unmodified upstream kernel), opensource drivers etc.

No, BUT: it is hard to find an ARM-board that runs with a vanilla upstream kernel.

The sources for all ODROID-boards can be found here: https://github.com/hardkernel/linux . The patches are well-organized and as well as with the RPi (I own two of them= they try to get things upstream slowly. You can of course create an ebuild for the kernel-sources if you want.

About the GPU-drivers: I honestly didn't even bother to get them running. Android on the -U2 uses the binary drivers for the Mali-GPU. Some guys managed to get the Open-Source "lima" drivers to work with Ubuntu but since I run it headless anyways I didn't care.

It seems that the link to your images thread on odroid forum is no longer active/disabled.. Could you please upload them (or instructions/caveats/gotchas) somewhere else? I might also be able to host those for you as well.